1. Field of the Invention
The invention generally relates to a backlight module, and in particular, to a backlight module capable of providing a plane light source having good light uniformity.
2. Description of Related Art
In a traditional backlight module, in order to provide a plane white-light source, disposition of light emitting devices beside a light incident surface of a light guide plate may be disposing a red light emitting diode (LED) device, a green LED device, and a blue LED device beside the light incident surface in sequence. Therefore, red light, green light, and blue light provided respectively by the red LED device, the green LED device, and the blue LED device are mixed, thus generating white light.
However, as a light beam provided by an LED device has a property of high light directivity, light beams generated respectively by an LED device disposed at an outermost side beside the light incident surface of the light guide plate and an adjacent other LED device may not have a good light mixing effect, thus causing a phenomenon of red shift, green shift, and blue shift to occur at a corner of a light exit surface of the light guide plate. For example, if the light emitting device at the outermost side is a red LED device, an optical field distribution of red shift correspondingly occurs at the corner of the light exit surface of the light guide plate, such that the light uniformity of a plane light source provided by the backlight module is lowered. In other words, it is necessary to improve the light uniformity of a plane white-light source provided by a backlight module employing a traditional structure.
Taiwan Patent Publication No. 201024853 discloses an LED backlight module, and the backlight module includes an LED light source, a light guide plate, and a reflective bottom plate. A groove is disposed on the light guide plate at a position corresponding to the above of the LED light source, and is provided with a semi-transmissive and semi-reflective film. In addition, part of the light emitted from the LED light source may penetrate the semi-transmissive and semi-reflective film and is then guided out by the light guide plate, and the other part of the light may be reflected by the semi-transmissive and semi-reflective film to the bottom plate for being recycled. Though this disposition may alleviate the problem of poor light uniformity of the backlight module, the part of the light that directly penetrates the semi-transmissive and semi-reflective film has a relatively centralized light intensity, and thus a relative uniform light source may not be provided. In addition, a red LED, a blue LED, and a green LED may be employed as the LED light source.